Not ALL manual shift transmissions can be towed four down!
Some are splash lubricated. When the engine is not running, the transmission is not getting lubricated. Towing such a transmission can (and eventually will) cause severe damage to the bearings.
the applicable section of the Owners Manual is usually labelled "Recreational Towing (towing behind a Recreational Vehicle)". If the book does not have such a section, there is a better than average chance that such towing is not recommended. Tow the vehicle at your own risk.
Good luck.